1. Field of the Invention
The present invention relates to a circuit board applied for a battery pack detachable from a portable electronic apparatus such as a portable telephone and a note type personal computer for example, and a method for producing the circuit board.
The present invention also relates to a circuit board module used for a portable telephone, etc. for example and applied for a battery pack with a built-in cell for a battery, and to a method for producing the circuit board module.
2. Description of the Related Art
In conventional ways, a battery pack with a buil-in cell for battery such as a lithium ion battery, etc. has been provided for a portable telephone and a note type personal computer for example, and the battery pack is detachable from main body of the portable telephone and the like. By using the above battery pack, the above portable telephone and the like can be used for certain time without being supplied power voltage from a commercial power source.
FIG. 5 is a perspective view showing an example such the battery pack and FIG. 6 is a perspective view showing an example of a circuit board installed in the battery pack. The battery pack P provides a case 1 made of resin and the case 1 installs a circuit board 2 connected to a battery cell not shown.
On the circuit board 2, a wiring pattern not shown is formed, and plural external terminal portions 4 are formed on lands 6 formed as a part of the wiring pattern by joining roughly square shaped Ni pieces 21 cut from hoop material of pure Ni for example. The circuit board 2 is supported along inside of the case 1 so that the external terminal portions 4 expose out through openings 5 (see FIG. 5) formed on the surface of the case 1. The battery pack 1 is possible to connect electrically to the main body of the portable telephone (not shown) by contacting connector pins (not shown) formed at the main body.
At the circuit board 2, connecting terminals 3 made of metal piece for connecting to the battery cell are provided. The circuit board 2 supplies electric power to the above main body and charges the battery cell through the connecting terminals 3 and each external terminal portion 4. The circuit board 2 includes a protecting circuit (not shown) for preventing over charge and over discharge in the battery cell.
The external terminals 4 are formed by joining the Ni pieces 21 on the lands 6 of the wiring pattern as described above, or by plating the above Ni pieces 21 with Au for example.
However, the above Ni pieces 21 have comparatively high in contact resistance so that contact failure occasionally happens at connection to the main body of the portable telephone. Pure Ni is frequently used for the Ni pieces 21 and there is a problem that cost of the pure Ni increases and soldering on the lands 6 of the wiring pattern is difficult. Then, it is considerable that the external terminals 4 are formed by plating on the lands 6 of the wiring pattern with hard Au. However, there is a problem that Au has bad yield because Au is easy to have a scratch on the surface thereof.
Further, a battery pack with a built-in cell for battery such as a lithium ion battery, etc. has been provided for a portable telephone and a note type personal computer for example, and the battery pack is detachable from main body of the portable telephone and the like.
In the above battery pack, a circuit board module is assembled, which is constructed with a battery case for storing the cell for battery and a circuit board including a circuit for supplying electric power to the main body of the portable telephone and preventing over-discharge and over-charge. The battery case and the circuit board are connected electrically and/or mechanically by a roughly long rectangular joint body which hoop material of Ni, for example, is cut to the designated size.
In recent year, Al is frequently used for material of the battery case responding to a request of lightening a portable telephone, and so on. However, since the join body is made of Ni, desirable contact between metals can not be obtained in connection between the battery case and the joint body so that the connection does not become stable connecting state.
Then, so called clad material bonded with metal body consisting of different metal materials each other for connection between the battery case 121 and the circuit board 122 as shown in FIG. 19 and FIG. 20. That is, the above-mentioned clad material is stood between the battery case 121 and a joint body 123 so as to joint the both. Concretely, when material of the battery case 121 is Al for example, a clad material in which metal material of one metal layer 124a is Al and metal material of other metal layer 124b is Ni as a joining member 124 is provided, and one metal layer 124a side of the joining member 124 is contacted to side face 121a of the battery case 121. Then, the battery case 121 and the joining member 124 are joined by spot welding for example so as to integrate.
By such the way, other metal layer 124b side made of Ni of the joining member 124 exposes outside, and to other metal layer 124b of the joining member 124, one end portion 123a of the joint body 123 made of Ni being the same metal material as the metal layer is joined by welding. Other end portion of bent joint body 123 and a pad portion 125 of the circuit board 122 are connected by soldering. Thus, the battery case 121 and the joint body 123 have good connection between metals and stable connecting state.
However, in the circuit board module of the above construction, when the circuit board 122 is connected to the battery case 121, the joining member 124 made of clad material and the joint body made of Ni must be used each other. Accordingly, since parts cost becomes high because of many parts and welding operation for joining the joining member 124 to the battery case 121 or joining the joint body 123 to the joining member 124 takes time, there has been a problem that operation cost increases.
The invention is considered on the above-mentioned circumstances, the problem is to provide a circuit board decreasing parts cost and removing problems such as contact failure, a battery pack using the circuit board, and a method for producing the circuit board.
To solve the above problems, the invention has the following technical means.
According to a battery pack concerned in a first aspect of the invention, the battery pack comprises a board and an external terminal portion formed on the board for connecting to an external apparatus wherein the external terminal portion is constructed by clad material that plural metal layers having different metal material each other are laminated. Concretely, the external terminal is constructed by a first metal layer made of Cu, a second metal layer formed on the first metal layer and made of stainless steel, and a third metal layer formed on the second metal layer and made of Ni alloy.
According to the above construction, decrease of parts cost at the circuit board can be designed because the clad material constructed as above-mentioned for the external terminal portion provided in the battery pack instead of Ni piece expensive generally used for the conventional construction.
Since Cu is used for the first metal layer of the external terminal portion and the first metal layer is joined to the land of the wiring pattern formed on the board and made of Cu foil for example, contact between these metals becomes good state and adhesiveness of the external terminal portion to the wiring pattern can be raised. Since stainless steel is used for the second metal layer, corrosion resistance of whole of the external terminal portion can be raised and rigidity can be made large. For example, by setting thickness of the second metal layer to suitable value, bend at soldering the above-mentioned clad material on the circuit board by reflow process can be depressed. Since Ni alloy is used for the third metal layer being as the highest layer, the surface does not have scratch like as plating by Au for example and yield can be removed.
According to a battery pack concerned in a second aspect of the invention, the battery pack comprises a case, a battery installed in the case, and a circuit board connected to the battery and according to the first aspect, wherein the case has an opening and the circuit board is located so that the external terminal portion faces outside from the above-mentioned opening.
According to the above-mentioned construction, the external terminal portion of the circuit board is constructed by clad material, the external terminal portion is formed so as to face outside from the opening, and is connected to the main body of the external apparatus, for example, the portable telephone. Because of that, good connecting state can be kept without occurring contact failure to the main body of the portable telephone and the battery pack of low cost can be provided.
According to a method for manufacturing a circuit board concerned in a third aspect of the invention, the method for manufacturing a circuit board having a board and an external terminal portion formed on the board for connecting to an external apparatus, comprising a process making a laminated member by laminating plural metal layers having different metal material each other, and a process forming a wiring pattern on the surface of the board and forming the external terminal portion by providing the laminated member on a pad of the wiring pattern.
According to the method for manufacturing the above-mentioned circuit board, the circuit board concerned in the first aspect of the invention is realized easily, and advantageous effect similar as the effect in the circuit board concerned in the first aspect of the invention can be obtained.
Further, the invention is considered on the above-mentioned circumstances, the problem is to provide a circuit board module connecting a battery case and a circuit board with easy construction and low cost, and a method for producing the circuit board module.
To solve the above problems, the invention has the following technical means.
According to a circuit board module concerned in a fourth aspect of the invention, the circuit board module is characterized by comprising a battery case storing a battery, a circuit board for carrying out charge and discharge of the above-mentioned battery, and a joint member for connecting the battery case and the circuit board electrically and/or mechanically, wherein the above-mentioned joint body is constructed by clad material that plural metal layers having different metal material each other are laminated. Concretely, at least one metal layer of the metal layers of the joint body consists of the same kind of metal material of the battery case. The joint body is constructed by a first metal layer made of Ni and a second metal layer made of Al.
According to the construction, since the joint body for connecting the battery case and the circuit board is constructed by clad material that plural metal layers made of Ni and Al are laminated, when the battery case is made of Al for example, the battery case and the circuit board can be joined using welding for example by contacting the second metal layer side made of Al of the clad material. The first metal layer side made of Ni of the clad material can be joined on the circuit board by soldering for example. That is, since the battery case and the circuit board can be connected directly though the joint body made of clad material there is no need to use conventional joining member so as to design decrease of parts cost. Since there is no need to weld the above-mentioned joining member to the battery case, welding time is removed so as to design decrease of operation cost.
According to a preferable mode for carrying out, thickness ratio of the first metal layer and the second metal layer of the joint body is about 1:1 to about 1:2. As above-mentioned, when the joint body is joined on the circuit board by soldering using reflow process for example, the joint body happens to bend by heat at reflow. This is caused by difference of linear expansion coefficient to temperature change at each metal material because of laminating different metal materials each other though it depends on size, shape, and the like of the joint body. That is, since Al of the second metal layer is comparatively larger than Ni of the first metal layer in the above-mentioned linear expansion coefficient, Al expands comparing with Ni and the joint body bends so that the second metal layer covers the first metal layer.
Then, in the invention, bent of the joint body is depressed by setting thickness ratio of both metal layers as the above-mentioned. That is, because elastic coefficient of Ni is generally larger than that of Al, namely Ni is harder than Al, as the result. Ni acts to compress elastically Al so as to depress expansion of the second metal layer made of Al. Thus, bent of the join body can be depressed. Therefore, the joint body can be soldered well on the circuit board without occurring soldering failure even at reflow process.
According to another preferable mode for carrying out of the invention, the joint body is roughly rectangle shape and is used being bent at the designated position in longitudinal direction. Even by this, bent of the joint body at reflow is depressed. That is, the joint body has bent at whole length of longitudinal direction because of difference of linear expansion coefficient to temperature change of difference metal material each other as describe above. Then, by previously bending the join body at the designated position in longitudinal direction before joining to the battery case and the circuit board, region generating bent is made narrow being separated at bent portion. Because of that, since degree of bent at the narrowed region becomes small comparing with bent at whole length of longitudinal direction so as to depress further bent of the joint body.
According to a method for mounting a circuit board module concerned in a fifth aspect of the invention, the method is characterized by that the circuit board module has a battery case, a circuit board for carrying out charge and discharge of the battery, and a joint body for connecting the battery case and circuit board electrically and/or mechanically, further uses the joint body concerned in the fourth aspect of the invention, and comprises a process soldering the first metal layer side of one end of the joint body at a terminal portion formed on the circuit board by reflow process, and a process welding the second metal layer side of the other end of the joint body.
According to the method for manufacturing, the circuit board module concerned in the fourth aspect of the invention is realized by the method for manufacturing, and advantageous effect similar as the effect in the above-mentioned circuit board module can be obtained.
Another characteristic and advantages of the invention will be made clear by detailed description of below referring attached figures.